1. Field of the Invention
The present invention relates generally to fluid flow measurement, and more particularly, but not by way of limitation, to turbine blade improvements for a flow meter.
2. Brief Description of the Prior Art
The size and complexity of fluid flow meters in the past have precluded the use of a flow meter which is disposed at the point of delivery where a fluid is dispensed. Further, flow meters with normal turbine blades used a flat blade profile of machined metal, which is expensive. Also, the high cost of existing self-contained battery powered equipment limited this type of equipment for use by an average consumer.
In the past there have been various types of flow meters with different types of read-out counters and blade designs. These types of flow meters are disclosed in the following U.S. Patents: Quesinberry U.S. Pat. No. 3,329,021; Belle U.S. Pat. No. 3,370,465; Gass et al U.S. Pat. No. 3,774,448; Kalotay, et al. U.S. Pat. No. 3,823,310; Onoda U.S. Pat. No. 4,265,127; Van Anden U.S. Pat. No. 128,338; Waugh U.S. Pat. No. 3,084,545; Potter U.S. Pat. No. 3,238,776; Clinton U.S. Pat. No. 3,757,578; Lauter, Jr. U.S. Pat. No. 3,452,593; Boyd U.S. Pat. No. 3,534,602; Lui et al. U.S. Pat. No. 3,945,253; and Ikeda et al. U.S. Pat. No. 4,253,341.
Boyd U.S. Pat. No. 3,623,835 teaches a magnetic flow meter which has a nonmagnetic housing with a passageway in which is positioned a turbine rotor. The turbine rotor has a pair of oppositely disposed vanes made of a nonmagnetic metal with magnetic plugs near the vane tips for inducing a signal in a detection coil.
The vanes of U.S. Pat. No. 3,623,835 are typically shaped with little regard to the flow dynamics of the vane profile. Adamtchik, U.S. Pat. No. 2,524,870, does teach a curved blade or vane on a screw wheel or the like. The Adamtchik rotor blade, termed an "aerofoil", has a profile which increases continuously from hub to tip for the purpose of reducing stress. And while others have considered flow efficiency of turbine blades, such as Riollet U.S. Pat. No. 3,529,631, such thought has largely been for the purpose of drag efficiency and not to measurement accuracy. Other prior art turbine blade designs are presented by Back, U.S. Pat. No. 1,719,415; Bristol et al., U.S. Pat. No. 3,332,500; Sparling, U.S. Pat. No. 2,770,131; Lahaye, U.S. Pat. No. 3,686,948; and Stapler, U.S. Pat. No. 4,114,440. Even the marine propeller of Kress, U.S. Pat. No. 4,073,601, when considered in the teachings of the other patents mentioned, does not provide any adequate teaching as to the desired blade profile for a flow meter which has a high measurement accuracy over a wide range of fluid flow and viscosity changes.
None of the patents mentioned hereinabove specifically discloses the unique structure and advantages of the improved turbine blade of the present invention used in a turbine flow meter.